The invention is directed to a circuit arrangement for the digitalization of the angle of rotation .phi. of a rotatable device which is operated with fa rotations per second, employing auxiliary voltages which are modulated with the sin .phi. and the cos .phi. of a fundamental frequency fo, and which, by means of additional circuit elements, are transformed into a counter pulse train which represents the angle of rotation, in which n pulses correspond to the angle of rotation of 360.degree..
German OS 2 054 553 (UK Patent Application 54305-69, filed Nov. 5, 1969) describes a device for deriving the angular position of a rotatable device, employing two auxiliary voltages, one of which fulfills the function U1 = sin .phi. .sup.. sin2.pi..sup.. fo.sup.. t, while the second voltage fulfills the function U2 = cos .phi. .sup.. cos2.pi..sup.. fo.sup.. t, wherein .phi. is the angle of rotation of the rotatable device and fo is the frequency of the auxiliary voltage of the angle indicator. In such known arrangement, a series of pulses are formed, utilizing suitable scanning circuits, from the analogue signal of the auxiliary voltages U1, U2 and a 90.degree. phase shift of the series of pulses is effected. In addition thereto, a reference phase signal is produced and is compared with the signal derived from the original signal. Consequently, the known arrangement requires a very high outlay for effecting a determination of an angle transformation.